[Objective] This study aimed to investigate the combined control effects of endophytic bacteria at different growth stages against cotton Verticfllium wilt and pro- vide a new strategy for the biocontrol of other soil-borne diseases. [Method] Endophytic bacteria with high resistance against Verticillium wilt were isolated from seedling, squaring and boll-setting cotton vascular, respectively. Their 16S rDNA se- quences were detected for comparative analysis. Three biocontrol strains were se- lected and identified, whose colonization roles in cotton plants were explored. The control efficiency was determined with indoor and field experiments. [Result] Accord- ing to the 16S rDNA sequence homology, the three strains were identified as Paeni- bacillus polyrnyxa YUPP-8, Paenibacillus xylanilyticus YUPP-1 and Bacillus subtilis YUPP-2, respectively. Results of colonization assessment showed that three strains all could be successfully colonized in cotton vascular. However, application amount had a positive effect on the number of colonized biocontrol bacteria in cotton, strain YUPP-8 had the largest number of colonized biocontrol bacteria in seedling period, strain YUPP-1 had the largest number of colonized biocontrol bacteria in squaring period, and strain YUPP-2 had the largest number of colonized biocontrol bacteria in boll-setting period. Indoor pot experiment showed that cotton plants in combined bio- control bacteria treatment group were not infected in flowing period, while Verticillium wilt morbidity rate of cotton treated with single strain in seedling period were 6.7% （YUPP-8）, 6.7% （YUPP-1） and 13.3% （YUPP-2）; however, Verticillium wilt morbidity rate wilt of the control reached 80%. Field experiment conducted during 2010-2011 showed that the combined application of three strains had better effect than separate application; specifically, Verticillium wilt morbidity rate and disease index of cotton in boll-setting period with combined application of three strains in 2010 were 9.4% and 6.5, respect
